NAME

Git::Database::Role::ObjectReader - Abstract role for a Git backends that read objects

VERSION

version 0.007

SYNOPSIS

    package MyGitBackend;

    use Moo;
    use namespace::clean;

    with
      'Git::Database::Role::Backend',
      'Git::Database::Role::ObjectReader';

    # implement the required methods
    sub get_object_attributes { ... }
    sub all_digests           { ... }

DESCRIPTION

A backend doing the additional Git::Database::Role::ObjectReader role is capable of reading data from a Git repository to produce objects or return information about them.

METHODS

has_object

    # assuming 4b825dc642cb6eb9a060e54bf8d69288fbee4904 (the empty tree)
    # is in the database and 123456 is not

    $kind = $backend->has_object('4b825dc642cb6eb9a060e54bf8d69288fbee4904');  # true ('tree')
    $kind = $backend->has_object('4b825d');    # also true ('tree')
    $kind = $backend->has_object('123456');    # false ('')

Given a digest value (possibly abbreviated), has_object returns a boolean indicating if the corresponding object is in the database.

As a convenience, if the object exists in the Git database, the true value that is returned is its "kind".

get_object

    # a Git::Database::Object::Tree representing the empty tree
    $tree = $backend->get_object('4b825dc642cb6eb9a060e54bf8d69288fbee4904');
    $tree = $backend->get_object('4b825d');    # idem

    # undef
    $tree = $backend->get_object('123456');

Given a digest value (possibly abbreviated), get_object returns the full object extracted from the Git database (one of Git::Database::Object::Blob, Git::Database::Object::Tree, Git::Database::Object::Commit, or Git::Database::Object::Tag).

Returns undef if the object is not in the Git database.

get_object_meta

    # ( '4b825dc642cb6eb9a060e54bf8d69288fbee4904', 'tree', 0 );
    ( $digest, $kind, $size ) = $backend->get_object_meta('4b825d');

    # ( '123456', 'missing', undef )
    ( $digest, $kind, $size ) = $backend->get_object_meta('123456');

Given a digest value (possibly abbreviated), return a list containing the complete digest, the object type and its size (if the requested object is in the database).

Otherwise it returns the requested $digest, the string missing and the undef value.

The default implementation is written using "get_object_attributes". Backend writers may want to implement their own for performance reasons.

REQUIRED METHODS

get_object_attributes

    # {
    #     kind    => 'tree',
    #     size    => 0,
    #     content => '',
    #     digest  => '4b825dc642cb6eb9a060e54bf8d69288fbee4904',
    # }
    my $attr = $backend->get_object_attributes('4b825d');

    # undef
    my $attr = $backend->get_object_attributes('123456');

Given a digest value (possibly abbreviated), return a hash reference with all the attributes needed to create a new object (if the requested object is in the database). This method is typically used by "get_object" to create the actual object instance.

Otherwise return the undef value.

all_digests

    # all the digests contained in the Git database
    my @sha1 = $backend->all_digests();

    # filter by kind
    my @trees = $backend->all_digests('tree');

Return all the digests contained in the Git object database. If a kind argument is provided, only return the digests for that specific object kind.

Depending on the underlying implementation, this may return unreachable objects.

AUTHOR

Philippe Bruhat (BooK) <book@cpan.org>.

COPYRIGHT

Copyright 2016 Philippe Bruhat (BooK), all rights reserved.

LICENSE

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

cpanm Git::Database

perl -MCPAN -e shell
install Git::Database